In a Time Division Multiple Access (TDMA) based wireless avionics system, a 4235-4400 MHz frequency spectrum may be shared by wireless avionics devices, and an aircraft's Frequency-Modulated Continuous Wave (FMCW) Radio Altimeter (RA). The radio altimeter transmits a radio frequency signal and looks for a corresponding return signal, continuously sweeping the signal frequency back and forth across the frequency spectrum in a see-saw pattern. For some wireless avionics devices, that same spectrum is used in a TDMA fashion divided into a fixed number of timeslots over a frame period. The frequency spectrum is divided into a number of channels, and timeslots for using those channels are allocated to wireless avionic devices in such a way as to allow them to communicate with the other nodes of the wireless avionic system and not interfere with the radio altimeter.
To implement such a TDMA scheme and avoid signal collisions, wireless avionic devices need to be synchronized within a required amount of accuracy to guarantee that transmissions from the wireless avionic devices will not interfere with each other or with the radio altimeter. A wireless avionics device in this scheme cannot transmit until it is synchronized with the other wireless avionics devices using this scheme.
In many conventional systems, wireless avionics devices are synchronized by updating their slot time with a computed delay based on a pre-computed correction factor. Further, in some conventional systems, the pre-computed correction factor is based on factory settings and stored in a memory in the wireless avionics device.
For the reasons stated above and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the specification, there is a need in the art for alternate systems and methods to compute correction factor for unsynchronized wireless avionic devices in the presence of a FMCW radio altimeter.